Method of venting a stylographic pen

ABSTRACT

A vent system for a tube writing pen wherein the vent consists of a longitudinally adjustable capillary tube extending within the writing fluid reservoir and venting at varying predetermined depths in the writing fluid. The upper end of the capillary tube is open to atmospheric pressure.

[ June 26, 1973 ili ted States Patent 1 Danjzcek et al.

[56] References Cited UNITED STATES PATENTS METHOD OF VENTING A STYLOGRAPHIC PEN Inventors: William E. Danjzcek; Jean Pierre FOREIGN PATENTS OR APPLICATIONS 310 6/1900 Great Leuenberger, both of Easton;

Fortunate J. Micale; Ralph W. Wagner, both of Bethlehem, all of Pa.

Assignee: Koh-I-Noor Rapidograph, Inc.,

Primary ExamineF-Lawrence Charles Attorney--David l-l. Semmes Bloomsbury, NJ.

[22] Filed:

[57] ABSTRACT A vent system for a tube writing pen wherein the vent Sept. 30, 1971 I [21] Appl. N0.: 185,020

consists of a longitudinally adjustable capillary tube extending within the writing fluid reservoir and venting at varying predetermined depths in the writing fluid. The upper end of the capillary tube is open to atmospheric pressure.

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' sum 1 or 2 INVENTORS .WILLIAM E. DANJZC JEAN PIERRE E RGER TUNATO J. ALE PH W. WAGNER ATTORNEY 1 METHOD OF VENTING A STYLOGRAPI-IIC PEN BACKGROUND OF THE INVENTION 1. Field of the Invention It is common to vent stylographic writing pens through a spiral venting channel which is built into the nib..This venting channel communicates with the main ink reservoir via a hole in the upper end of the spiral venting channel. The spiral venting channel is normally cut into the same surface that also carries the tightly pitched screw threads which are provided for screwing the writing head into the body of the writing pen. This conventional arrangement has several consequences such as: (a) two intersecting threads of difference pitch, namely, the spiral venting channel and the screw thread must be cut into the nib, necessitating these additional production steps; and (b) the relatively short venting channel communicates with the outside air which may cause, even with the slightest neglect, the air to dry and block the venting channel, necessitating unscrewing the nib frequently for cleaning.

2. DESCRIPTION OF THE PRIOR ART Prior art searching has developed the following prior U.S. Pats. Nos.: Cross RE 9,890; Mackinnon 2l7,888; Nimmo 226,660; Luker 1,937,660.

This prior art, although suggesting the extension of hollow venting tubes from the pen top into the ink reservoir, does not suggest any method of longitudinally varying the position of the vent tube within the ink reservoir. Note, especially Mackinnon showing the air tube G extending from the top of the ink reservoir downward into the reservoir and terminating by a small lateral opening G above a valve F.

Nimmo shows a vent tube extending above the top of the pen. However, Nimmo is not explicit as to the positioning of the tube within the ink reservoir. Cross does suggest an air tube F which is longitudinally positionable within the pen. However, the Cross venting orifice F is positioned in the reservoir above the ink. Luker shows the employment of an adjustable venting stem 21 having a venting orifice 24 above the ink reservoir.

SUMMARY OF THE INVENTION This advanced method for venting is a capillary tube described herein which enables equalization of pressure without the conventional spiral venting channel and which has certain additional advantages. Applicants capillary venting eliminates the need for the spiral venting channel, as well as the need for a separate threaded nib. The vent system, as described in this application, allows the body and the nib to be manufactured asone single piece which simplifies construction and reduces manufacturing cost. The venting system is constructed to enable control of the hydrostatic head, which is all-important for controlling the rate of ink flow during the course of use and for preventing the danger'of dripping. By increasing the magnitude of the hydrostatic head, the rate of ink flow can be regulated with greater accuracy for increased writing speeds than have been possible with conventional pens. This is, also, of importance in computerized drafting where high speeds of writing are required.

BRIEF DESCRIPTION OF THE DRAWINGS:

' tional construction;

FIG. 2 is a vertical sectional view of the complete pen according to applicants construction which shows a one-piece design of the body and the nib directly attached to the writing fluid reservoir and supporting the capillary vent within the writing fluid reservoir;

FIG. 3 is an enlarged vertical sectional view of the tip of the writing tube showing in phantom the writing fluid drops in various stages of growth;

FIG. 4 illustrates a first modified capillary tube having loops for prevention of spilling ink from reservoir;

FIG. 5 illustrates a second capillary tube modification; and

FIG. 6 shows a threaded capillary located at the bottom of the ink cartridge 25.

DESCRIPTION OF THE PREFERRED EMBODIMENTS:

In FIG. 1, there is illustrated a conventional tube writing pen of the type embodying a nib 10, an ink reservoir 12, and a tubular point 14 mounted within the nib. A spiral venting channel 18 may be cut into the tightly pitched screw threads 16 which are provided for screwing the writing head into the body of the writing pen. A vent 15 may extend from the spiral venting channel 18 into the reservoir 12.

In FIG. 2, applicants pen is illustrated as embodying a one-piece body and nib 30 supporting a tubular point 22 at one end and enclosing, at the other end, ink reservoir cartridge 32. Manifestly, point 22 may have other than a circular cross-section. A reciprocal weight 34 may have a cleaning wire 36 extending into the writing tube 22. A safety plug 38 may be formed as a cage over the upper end of weight 34, and a clamping ring 40 may be used to secure the reservoir cartridge assembly to the shoulder of the one-piece body and nib 30. A longitudinally reciprocal capillary venting tube may be supported within cartridge 32, such that its lower end is movable within the ink reservoir and its outer end 42 communicates with the outer atmosphere above the top of the ink cartridge.

Critical aspects of applicants pen are depicted in FIG. 2 where the symbols included may be defined as:

h depth of capillary tube bottom end 42 in writing P atmospheric pressure P, pressure in writing fluid at depth h P pressure in enclosed chamber above writing x distance from capillary tube bottom end 42' (20) to the lower tip of the writing tube (22) A air bubble at the bottom of capillary (20) at depth h in the writing fluid B drop of writing fluid at the tip of the writing tube The distribution of forces within the body of applicants pen has been constructed to allow definition in accordance with the hydrostatic head and the LaPlace Equation, given below, which predicts change in pressure across a curved liquid/gas interface:

r= radius of curvature of the curved liquid/gas interface A P change in pressure across this curved interface.

For the case of a bubble (A) forming on the bottom end 42 of the capillary (20), see FIG. 2, the AP across this bubble defined by applicant in his present construction according to the LaPlace Equation given above where:

r radius of curvature of the bubble itself A P P P Therefore g acceleration due to gravity, 980cm/sec. Equation 2 and 3 may be solved for P to give:

Combining the above two equations results in:

2 0 v/m g The total hydrostatic head, F, seen by the tip of the writing tube may be defined as:

F= (g (11+ (P P Equation 7 may be combined with Equation 6 to give:

F t gy/m Equation 8 has been applied by applicant to define the hydrostatic head of the writing fluid at the point of contact with the writing media in terms of the physical parameters of the pen and the physical properties of the writing fluid. Thus, the magnitude of the total hydrostatic head determines with a high degree of accuracy the velocity of flow of the writing fluid.

The important practical consequences of the above is the prevention ofthe spontaneous formation of drops at the lower end of the writing tube 22. Applicant, for

the first time, provides in his construction independent close control of ink flow, particularly as compared to all earlier systems. Furthermore, this construction provides control of ink flow independently of the amount of writing fluid in the reservoir, as long as the bottom end 42 of the capillary is immersed within the writing fluid. Applicants construction controls (x) the distance from the bottom end of the capillary to the lower tip of the writing tube (22) and r, the radius of curvature of the bubble.

FIG. 3 shows the formation of a drop, at the lower tip of the writing tube, in three stages ofgrowth. The initial formation of the drop (1) results in the drop having a large radius of curvature. As the drop grows, the radius of curvature decreases to some minimum value (2) at which point it forms a hemisphere with the O. D. of the writing tube. Further growth of the drop can only occur by increasing the radius of curvature as shown in (3). Since the La Place Equation, Equation 1, predicts that the force necessary to maintain equilibrium across a curved interface is inversely proportional to the radius of curvature, then (2) in FIG. 3 represents the critical threshold which must be overcome for the drop to grow. Therefore, dripping will not occur provided the total hydrostatic head, Equation 8, is less than 2'y/r where r equals V2 0. D. of the writing tube. Therefore, dripping will not occur when:

8 WA/Q gm 7 In FIGS. 4 and 5, modified capillary tubes 20' and 20" are provided with convolute extensions so as to prevent dripping in the event that the pen is inverted.

In the FIG. 6 modification, the acutal venting of the capillary 26 into the ink reservoir occurs at A, whereas the capillary 26 communicates with the atmosphere through hole 23 in the ink cartridge at the top of the capillary 23. The component which forms the capillary 28 has an axial hole 21 through the center as to allow the ink reservoir 24 to be connected to the one-piece pen body and nib 27 and the writing tube 29. The main advantage of this configuration is that writing fluid may expand into the capillary 26 without dripping occurring at B, the tip of the writing tube, provided the distance between B and 23, i.e., x, is not greater than the maximum allowable value given in Equation 10 for a writing tube ofa given radius, r The same threaded capillary, of course, can be located at the top of the one-piece body and nib.

We claim:

1. Method of venting a stylographic pen of the type embodying an ink reservoir supported above a tubular writing point and having a tubular venting stem with a top extending outside and a bottom extending inside of the ink reservoir, comprising:

A. venting the reservoir through said vent stem; and

B. vertically reciprocating said vent stem bottom within the ink contained in said reservoir and with respect to the lower end of said writing point, such that ink flow through said lower end is regulated.

2. Method of venting a stylographic pen of the type embodying an ink reservoir supported above a tubular writing point and having a tubular venting stem with a top extending outside and a bottom extending inside of the ink reservoir, as in claim 1, including raising said vent stem bottom with respect to the lower end of said writing tube, so as to enhance ink flow.

3. Method of venting a stylographic pen of the type embodying an ink reservoir supported above a tubular writing point and having a tubular venting stem with a top extending outside and a bottom extending inside of the ink reservoir, as in claim 1, including lowering said vent stem lower end toward said writing tip bottom so as to inhibit ink flow.

4. Method of venting a stylographic pen of the type embodying an ink reservoir supported above a tubular writing point and having a tubular venting stem with a top extending outside and a bottom extending inside of the ink reservoir, as in claim 1, wherein said vent stem bottom end is reciprocated within said reservoir to prevent ink from dripping, according to the following fomrula:

F magnitude of the hydrostatic head p density of the writing fluid g acceleration due to gravity 980 cm/sec.

r radius of vent stem bottom tip x distance between vent stem bottom tip and the lower end of the writing point.

y surface tension of writing fluid.

5. A stylographic pen comprising:

A. a writing nib;

B. a tubular writing tip having its lower end extending through said writing nib;

C. an ink reservoir supported upon said nib and communicant with said pen tip; and

D. a capillary venting tube extending from the outside of said reservoir to the interior of said reservoir and having its lower end vertically adjustable with respect to the lower end of said writing tip.

6. A stylographic writing pen as in claim 5, said nib having lower portion conformed to support said writing tip and its upper portion conformed as a body to support said weight and wire assembly, as well as said ink reservoir.

7. A stylographic writing pen, comprising:

A. a writing nib;

B. a tubular writing tip having its lower end extending through the bottom of said nib;

C. an ink reservoir supported within said nib and communicant with said pen tip;

D. a threaded venting stern interconnecting the exterior of said pen and the interior of said reservoir and vertically adjustable within said reservoir, so as to vary the height of said venting stem interior and with respect to said writing tip; and

E. a weight and cleaning wire assembly supported intermediate said threaded venting stem and said nib, such that said cleaning wire extends reciprocably into said tubular writing tip. 

1. Method of venting a stylographic pen of the type embodying an ink reservoir supported above a tubular writing point and having a tubular venting stem with a top extending outside and a bottom extending inside of the ink reservoir, comprising: A. venting the reservoir through said vent stem; and B. vertically reciprocating said vent stem bottom within the ink contained in said reservoir and with respect to the lower end of said writing point, such that ink flow through said lower end is regulated.
 2. Method of venting a stylographic pen of the type embodying an ink reservoir supported above a tubular writing point and having a tubular venting stem with a top extending outside and a bottom extending inside of the ink reservoir, as in claim 1, including raising said vent stem bottom with respect to the lower end of said writing tube, so as to enhance ink flow.
 3. Method of venting a stylographic pen of the type embodying an ink reservoir supported above a tubular writing point and having a tubular venting stem with a top extending outside and a bottom extending inside of the ink reservoir, as in claim 1, including lowering said vent stem lower end toward said writing tip bottom so as to inhibit ink flow.
 4. Method of venting a stylographic pen of the type embodying an ink reservoir supported above a tubular writing point and having a tubular venting stem with a top extending outside and a bottom extending inside of the ink reservoir, as in claim 1, wherein said vent stem bottom end is reciprocated within said reservoir to prevent ink from dripping, according to the following fomrula: F Rho g x - 2 gamma /rA Where: F magnitude of the hydrostatic head Rho density of the writing fluid g acceleration due to gravity 980 cm/sec.2. rA radius of vent stem bottom tip x distance between vent stem bottom tip and the lower end of the writing point. gamma surface tension of writing fluid.
 5. A stylographic pen comprising: A. a writing nib; B. a tubular writing tip having its lower end extending through said writing nib; C. an ink reservoir supported upon said nib and communicant with said pen tip; and D. a capillary venting tube extending from the outside of said reservoir to the interior of said reservoir and having its lower end vertically adjustable with respect to the lower end of said writing tip.
 6. A stylographic writing pen as in claim 5, said nib having lower portion conformed to support said writing tip and its upper portion conformed as a body to support said weight and wire assembly, as well as said ink reservoir.
 7. A stylographic writing pen, comprising: A. a writing nib; B. a tubular writing tip having its lower end extending through the bottom of said nib; C. an ink reservoir supported within said nib and communicant with said pen tip; D. a threaded venting stem interconnecting the exterior of said pen and the interior of said reservoir and vertically adjustable within said reservoir, so as to vary the height of said venting stem interior and with respect to said writing tip; and E. a weight and cleaning wire assembly supported intermediate said threaded venting stem and said nib, such that said cleaning wire extends reciprocably into said tubular writing tip. 